Co-reporter:Xiulong Mao;Guimin Lu;Jianguo Yu;Yuzhu Sun;Yanxia Xu
Industrial & Engineering Chemistry Research November 12, 2014 Volume 53(Issue 45) pp:17625-17635
Publication Date(Web):Publication Date (Web): October 20, 2014
DOI:10.1021/ie5030134
The effects of metal ions such as Na+, K+, Mg2+, Cu2+, Al3+, and Fe3+ on the crystal morphology and size of calcium sulfate whiskers in aqueous HCl solutions were investigated. The average diameter, aspect ratio, length, crystal water content, phase composition, and elemental composition of the products were determined and compared. When the concentration of monovalent Na+ or K+ ions was low, with the increase in the ion concentration, the average diameter increased and the aspect ratio decreased. However, with further increase in the ion concentration, the average diameter decreased. The presence of divalent Mg2+ or Cu2+ ions increased the crystal diameter and length. All the products were calcium sulfate hemihydrate in the presence of Na+, K+, Mg2+, or Cu2+ ions within the studied concentration range. The presence of trivalent Al3+ or Fe3+ ions at low concentrations resulted in bigger and shorter crystals; furthermore, at higher ion concentrations, partial phase transformation from calcium sulfate hemihydrate to calcium sulfate dihydrate was induced. Among the metal ions investigated, only Na+ ions were found be incorporated into the crystals.
Co-reporter:Xiulong Mao;Guimin Lu;Yanxia Xu;Jianguo Yu;Yuzhu Sun
Industrial & Engineering Chemistry Research May 6, 2015 Volume 54(Issue 17) pp:4781-4787
Publication Date(Web):2017-2-22
DOI:10.1021/acs.iecr.5b00585
The effect of cetyltrimethylammonium bromide (CTAB) on the crystal morphology and size of calcium sulfate whiskers in aqueous HCl solutions was investigated by combined experimental and molecular dynamics (MD) simulation studies. When CTAB was used, calcium sulfate whiskers with small diameters and high aspect ratios were obtained. The MD simulation results indicate that the experimental results can be attributed to the combined effect of the surface adsorption and inhibition of the solute diffusion of CTAB.
Co-reporter:Xingfu Song;Guoping Xiao;Kefeng Tong;Jianguo Yu
Industrial & Engineering Chemistry Research March 26, 2014 Volume 53(Issue 12) pp:4755-4762
Publication Date(Web):Publication Date (Web): March 5, 2014
DOI:10.1021/ie5002857
The rheological behavior and stability of Mg(OH)2 suspensions were studied in the presence of sodium polyacrylate with different molecular weights under conditions of different ionic strength and counterion valence (K+ and Mg2+). Rheological properties, optical absorbance, and zeta potential measurements were conducted on the Mg(OH)2 particle suspensions to assess the dispersing ability of the sodium polyacrylate dispersants. Adsorption isotherm measurements were applied to investigate the effect of counterions on the adsorption behavior. The results demonstrate that Mg2+ ions destabilize the Mg(OH)2 suspensions more dramatically than K+ ions due to the stronger screening effect and special complexation of Mg2+ ions and carboxyl groups. The effect of molecular weights of NaPA on the rheological properties becomes more pronounced at higher solid loading because the NaPA with a molecular weight of 15,000 g/mol increases the viscosity more obviously than NaPA with a molecular weight of 1200 g/mol. The calculation results of interparticle interaction by the Hamaker 2 program show that the suspensions can achieve good stability with sufficient NaPA dosage, which coincides with the optical absorbance measurement results.
Co-reporter:Guilan Chen, Xingfu Song, Yanxia Xu, and Jianguo Yu
Industrial & Engineering Chemistry Research June 21, 2017 Volume 56(Issue 24) pp:7100-7100
Publication Date(Web):May 23, 2017
DOI:10.1021/acs.iecr.7b00609
The effects of NO3– and SO42– ions on the H+ concentration in organic phase and crystal morphology of solid product nesquehonite (MgCO3·3H2O) in the coupled reaction–extraction–crystallization process were investigated. During the coupled process, the H+ concentration in organic phase increased with the increase in concentration of NO3– ions and decreased with the increase in concentration of SO42– ions, indicating that NO3– ions promoted the carbonization of MgCl2 while SO42– ions inhibited the same. The rodlike MgCO3·3H2O crystals became short and thick in the presence of both NO3– and SO42– ions. Energy-dispersive X-ray spectroscopy (EDS), inductively coupled plasma atomic emission spectroscopy (ICP-AES), and molecular dynamic simulation were used to clarify the mechanism by which impurity ions modified the structure. The results indicated that the NO3– and SO42– anions could be selectively adsorbed on the top facet (011̅) of MgCO3·3H2O, preventing the growth of crystal surfaces, which results in the decrease in length and increase in diameter of MgCO3·3H2O product. The morphology modification by NO3– ion was mainly due to the selective adsorption of NO3– ions. Both selective adsorption of ions and the incorporation of ions accounted for the morphology modification by SO42– ions.
Co-reporter:Xingfu Song;Guoping Xiao;Kefeng Tong;Jianguo Yu
Industrial & Engineering Chemistry Research June 17, 2015 Volume 54(Issue 23) pp:6115-6122
Publication Date(Web):2017-2-22
DOI:10.1021/acs.iecr.5b01294
The rheological behavior and stability of aqueous magnesium hydroxide (Mg(OH)2) suspensions were studied in the presence of comb-like polyelectrolyte, namely, sodium salts of poly(acrylic acid)-poly(ethylene oxide) (NaPAA–PEO) at high ionic strength. Rheological, sedimentation, and zeta potential measurements were conducted on Mg(OH)2 suspensions to assess the dispersing ability of NaPAA–PEO. The adsorption behavior of NaPAA–PEO on the surfaces of Mg(OH)2 particles was investigated by the adsorption isotherm measurements. The interparticle interactions were calculated by using the Hamaker 2 program to evaluate the effect of NaPAA–PEO dosage on the stability of suspensions. The results indicated that NaPAA–PEO, which is insensitive to ionic strength variation, could improve the salt-tolerance of Mg(OH)2 suspensions and provide effective electrosteric stabilization, thus facilitating the production process and application of Mg(OH)2 suspensions over broad range of ionic strength.
Co-reporter:Bo TANG, Yan-xia XU, Xing-fu SONG, Ze SUN, Jian-guo YU
Transactions of Nonferrous Metals Society of China 2017 Volume 27, Issue 7(Volume 27, Issue 7) pp:
Publication Date(Web):1 July 2017
DOI:10.1016/S1003-6326(17)60187-0
Inlet configuration is important parameter of hydrocyclones, which has great impact on the classification performance. The effects of inlet configuration on the precise classification were studied by computational fluid dynamics under various combinations of inlet diameter and inlet velocity. The results showed that a high sharpness of classification was achieved with specific inlet diameter and inlet velocity. The separation efficiency of the coarse particles by underflow significantly decreased when inlet had an oversize diameter owing to a stronger short-circuit flow. It is resulted from the chaotic flow and the stronger pressure gradient around the vortex finder. Meanwhile, a low separation efficiency of the fine particles by overflow was achieved when inlet velocity was high, which indicated a low sharpness caused by the overlarge centrifugal force.
Co-reporter:CHUNHUA DONG;EVERT JAN MEIJER;GUILAN CHEN
Journal of Chemical Sciences 2017 Volume 129( Issue 9) pp:1431-1440
Publication Date(Web):02 September 2017
DOI:10.1007/s12039-017-1357-4
The thermal dissociation of tri-n-octylamine hydrochloride (TOAHCl) was investigated using both the quantum chemical simulation and experimental methods. The pathway through which a mixture of tri-n-octylamine (TOA) and hydrogen chloride (HCl), rather than di-n-octylamine (DOA) and 1-chlorooctane, are produced has been determined through transition state (TS) search with Intrinsic Reaction Coordinate (IRC) calculations. Particularly, strong agreement between the experimental FTIR spectra and that of TOA demonstrates the same result for the first time. Moreover, the thermal dissociation of TOAHCl proceeds in two continuous steps, which is different from the low molecular mass amine hydrochlorides. The experimental enthalpy of the dissociation was 70.793 \(\hbox {kJ mol}^{-1}\) with DSC measurement which is very close to the density functional theory (DFT) calculation result 69.395 \(\hbox {kJ mol}^{-1}\). Furthermore, with the aid of DFT calculations, some other important thermochemical characteristics such as crystal lattice energy with the value of 510.597 \(\hbox {kJ mol}^{-1}\) were evaluated by means of Born–Fajans–Haber cycle.
Co-reporter:Guilan Chen, Xingfu Song, Chunhua Dong, Shuying Sun, Ze Sun, and Jianguo Yu
Energy & Fuels 2016 Volume 30(Issue 9) pp:7551
Publication Date(Web):August 1, 2016
DOI:10.1021/acs.energyfuels.6b01297
A novel coupled reaction–extraction–alcohol precipitation process was proposed to mineralize CO2 as MgCO3·3H2O directly by abandoned MgCl2. Rod-like crystal MgCO3·3H2O was obtained, and the conversion rate of MgCl2 increased sharply by using this novel coupled reaction–extraction–alcohol precipitation process. The effect of an added C1–C3 alcohol precipitation agent on the conversion rate of MgCl2 was in the following order: ethanol > isopropanol > n-propanol > methanol. Moreover, the optimal conditions for the highest conversion rate of MgCl2 by single-factor experiments were obtained as follows: initial concentration of MgCl2 solution is 2 mol·L–1, volume ratio of ethanol and aqueous phase is 2, mole ratio of N235 and aqueous phase is 2, volume ratio of diluent and N235 is 0.5, with a stirring rate of 300 r·min–1 at 298.15 K and at atmospheric pressure.
Co-reporter:Guilan Chen;Shuying Sun
Frontiers of Chemical Science and Engineering 2016 Volume 10( Issue 4) pp:480-489
Publication Date(Web):2016 December
DOI:10.1007/s11705-016-1603-1
Co-reporter:Jingcai Zhao;Yuzhu Sun;Bo Chen ;Jianguo Yu
Crystal Research and Technology 2015 Volume 50( Issue 4) pp:277-283
Publication Date(Web):
DOI:10.1002/crat.201400135
Batch reactive crystallization of calcium carbonate (CaCO3) from ammonium carbonate ((NH4)2CO3) and calcium sulfate (CaSO4) was investigated in the presence of magnesium (Mg2+) ions. It was observed that Mg2+ ions partly inhibited the conversion of CaSO4 into CaCO3. When the content of Mg2+ was less than 2%, the reduction in conversion rate of CaSO4 was less than 2%, and the effect of Mg2+ ions could be ignored. Effect of impurity on crystallization kinetics of CaCO3, including the growth rate and nucleation rate, was investigated. The results revealed that when Mg2+ ions content was less than 1%, Mg2+ could promote the growth of CaCO3 and inhibit the nucleation process, which was favorable for the filtration of CaCO3.When the content of Mg2+ ions was greater than 1%, Mg2+ inhibited the growth of CaCO3, which resulted in explosion nucleation and led to a large number of particles in the solution, which was unfavorable for the filtration of CaCO3. Based on the Bransom model, the particle size distribution equations of CaCO3 were established. X-ray diffraction patterns and scanning electron microscopy images exhibited the existence of spherical vaterite of CaCO3 due to the reaction of CaSO4 with (NH4)2CO3 under the effect of Mg2+ ions, which was inconsistent with the results reported in the literatures.
Co-reporter:Yunzhao Li;Guilan Chen
Frontiers of Chemical Science and Engineering 2015 Volume 9( Issue 4) pp:479-487
Publication Date(Web):2015 December
DOI:10.1007/s11705-015-1512-8
A coupled reaction-solvent extraction process was used to remove HCl from a simulated distiller waste. The extraction performances of various extractants and diluents were compared and the apparent basicity of N235 (a mixture of tertiary amines) in various diluents was determined. The best results were obtained using N235 and isoamyl alcohol as the extractant and diluent, respectively. The yield of HCl from the coupled extraction was 75% with this extraction system. The mechanisms for the removal of HCl in both the direct and coupled extractions were investigated. For the coupled extraction, the formation of an R3NHCl ion-pair complex was involved in the HCl removal. For the direct extraction, the mechanism involved the formation of hydrogen bonds at high concentrations of HCl.
Co-reporter:Yunzhao Li; Xingfu Song; Shuying Sun; Yanxia Xu;Jianguo Yu
Journal of Chemical & Engineering Data 2015 Volume 60(Issue 10) pp:3000-3008
Publication Date(Web):September 16, 2015
DOI:10.1021/acs.jced.5b00409
N235 in isoamyl alcohol solution acts as an efficient extraction system for the revovery of hydrochloric acid (HCl) at very low concentrations in a coupled reactive extraction–crystallization process. In this study, the extraction equilibrium of N235 + isoamyl alcohol + HCl + H2O system was investigated systematically. The formation of the extraction complex in the organic phase was determined by using the experimental data and it was confirmed to be (HCl)4(R3N)4(H2O)8. Further, the thermodynamic model was then established by using Pitzer equation to calculate the activities of all the species. The values of the interaction parameters obtained by regression are as follows: βR3N,4:4:8(org) = 2.8782 and β4:4:8,4:4:8(org) = 11.4764. The extraction equilibrium constant is ln K4:4:8 = 38.0274. The thermodynamic model was demonstrated to be reliable and suitable for the N235 + isoamyl alcohol + HCl + H2O system.
Co-reporter:Shu-Ying Sun, Jia-Li Xiao, Jin Wang, Xingfu Song, and Jian-Guo Yu
Industrial & Engineering Chemistry Research 2014 Volume 53(Issue 40) pp:15517-15521
Publication Date(Web):2017-2-22
DOI:10.1021/ie5004625
Orthorhombic LiMnO2 (o-LiMnO2), spinel Li1.6Mn1.6O4 precusors, and spinel H1.6Mn1.6O4 ion sieves were synthesized by a combination of controlled redox precipitation and solid-phase reaction. o-LiMnO2 was synthesized by a controlled redox precipitation using Mn(OH)2, LiOH, and (NH4)2S2O8. Spinel Li1.6Mn1.6O4 precursor was prepared by the heat treatment of o-LiMnO2. Further, an ion sieve (H1.6Mn1.6O4) was synthesized by the acid (HCl) treatment of Li1.6Mn1.6O4. The effect of redox precipitation and solid-phase reaction on the structure and ion-exchange property of the ion sieve was examined by powder X-ray diffraction, scanning electron microscopy, and Li+-selective adsorption measurements. The results showed that the ion sieve exhibited highly selective adsorption capacity for Li+ (3.88 mmol·g–1) from Qarhan salt lake brine, which was significant for the Li+ extraction from low-grade brine.
Co-reporter:Yanxia Xu, Xingfu Song, Ze Sun, Bo Tang, Ping Li, and Jianguo Yu
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 15) pp:5470
Publication Date(Web):March 21, 2013
DOI:10.1021/ie302081v
The air core is an important phenomenon in a hydrocyclone. The steady state of the air core plays a key role in the performance and separation efficiency of a hydrocyclone. The unsteady structure of the air core reflects the unsteady flow field and exacerbates this unsteadiness, thus affecting the steadiness and homogeneity of the flow field, which will lead to lower separation efficiency. The effects of the ratio of the vortex-finder diameter to the spigot diameter (Do/Du) on the steady state of the air core were studied by computational fluid dynamics in this paper. In this approach, the Reynolds stress model used to describe the turbulent fluid flow and the volume-of-fluid multiphase model simulated the interface between the liquid and air core. The results show that the steady state of the air core is mainly decided byDo/Du. Different ranges of Do/Du lead to different steady states of the air core. No air core appeared inside the hydrocyclone with a Do/Du of 1.2. The discontinuous ones occur when Do/Du enlarges to 1.6 and 1.8. Through the continuous air core grown in the hydrocyclone with a Do/Du larger than 1.8, the rules of the steady state were different. In addition, the operation conditions of the inlet velocity did not change the trend of the steady state of the air core in a certain hydrocyclone.
Co-reporter:Chen Yang, Xingfu Song, Shuying Sun, Ze Sun, Jianguo Yu
Advanced Powder Technology 2013 Volume 24(Issue 3) pp:585-592
Publication Date(Web):May 2013
DOI:10.1016/j.apt.2012.10.005
Abstract
In this study, nesquehonite MgCO3·3H2O whiskers with long length and high aspect ratio were synthesized through reactive crystallization, in which MgCl2 and Na2CO3 precipitated in the presence of sodium dodecyl sulfate (SDS). The effects of SDS concentration, reactive temperature and reactants concentration were investigated. SEM, XRD and FT-IR were used to character morphology and structure of the products. It was found that the presence of SDS in the mixed aqueous solution was an important parameter for the morphology and size of nesquehonite crystals. The morphology of nesquehonite crystals changed from rod-like to bundle-like with increasing SDS concentration. The average length of nesquehonite whiskers was about 87–180 μm while the aspect ratio was 18–45. The longest length reached 250 μm and the biggest aspect ratio was about 100. The reactive temperature and reactant concentration also affect the size even the crystal type. It is concluded that SDS was beneficial for oriented growth of one-dimensional nesquehonite whiskers based on the formation process of the nesquehonite whiskers. The possible mechanism of SDS in nesquehonite whiskers precipitation was ascribed to physical adsorption of SDS on the individual amorphous nanoparticles or crystallites. The critical point of oriented growth occurred when the SDS concentration was about 4.33 mM.
Co-reporter:Xingfu Song;Kefeng Tong;Shuying Sun
Frontiers of Chemical Science and Engineering 2013 Volume 7( Issue 2) pp:130-138
Publication Date(Web):2013 June
DOI:10.1007/s11705-013-1332-7
Magnesium hydroxide is an important chemical, and is usually obtained from seawater or brine via precipitation process. The particle size distribution of magnesium hydroxide has great effects on the subsequent filtration and drying processes. In this paper, micron-sized magnesium hydroxide with high purity, large particle size and low water content in filter cake was synthesized via simple wet precipitation in a mixed suspension mixed product removal (MSMPR) crystallizer. The effects of reactant concentration, residence time and impurities on the properties of magnesium hydroxide were investigated by X-Ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Malvern laser particle size analyzer. The results show that NaOH concentration and residence time have great effects on the water content and particle size of Mg(OH)2. The spherical Mg(OH)2 with uniform diameter of about 30 μm was obtained with purity higher than 99% and water content less than 31%. Furthermore, the crystallization kinetics based on the population balance theory was studied to provide the theoretical data for industrial enlargement, and the simulation coefficients (R2) based on ASL model and C-R model are 0.9962 and 0.9972, respectively, indicating that the crystal growth rate of magnesium hydroxide can be well simulated by the sizedependent growth models.
Co-reporter:Xingfu Song;Jingcai Zhao;Yunzhao Li
Frontiers of Chemical Science and Engineering 2013 Volume 7( Issue 2) pp:210-217
Publication Date(Web):2013 June
DOI:10.1007/s11705-013-1320-y
The decomposition mechanism of ammonium sulfate catalyzed by ferric oxide was investigated in this paper. The decomposition kinetics parameters were determined via a global optimization of the Kissinger iterative method using the non-isothermal thermogravimetric analysis data. The products and intermediates were synchronously characterized by X-ray diffraction and mass spectrometry. The obtained results indicate that the decomposition process of ammonium sulfate catalyzed by ferric oxide can be divided into four stages of which the activation energies are 123.64, 126.58, 178.77 and 216.99 kJ·mol−1 respectively. The decomposition mechanisms at the first and the fourth stage both belong to Mample power theorem, the second stage belongs to Avrami-Erofeev equation and the third belongs to contracting sphere (volume) equation. The corresponding pre-exponential factors (A) are calculated simultaneously.
Co-reporter:Jingcai Zhao;Ze Sun
Frontiers of Chemical Science and Engineering 2013 Volume 7( Issue 4) pp:447-455
Publication Date(Web):2013 December
DOI:10.1007/s11705-013-1370-1
This study on thermodynamic property of NH3-CO2-H2O system provided the basic data for ammonia carbonation. Simulations on vapor-liquid equilibrium (VLE) of ammonia carbonation with different physical properties were discussed in NH3-H2O and NH3-CO2-H2O systems, respectively. The results indicated that at low temperature (303.15 K-363.15 K) and pressure (0.1–0.4 MPa), the PR (Peng-Robinson) equation was suitable for the description of the thermodynamic state in NH3-H2O system. NRTL (Non-Random-Two-Liquid) series models were selected for NH3-CO2-H2O mixed electrolyte solution system. VLE data regression results showed that NRTL series models were suitable for describing thermodynamic properties of NH3-CO2-H2O system, because average relative error fitting with each model was about 1%. As an asymmetric electrolytes model in NRTL model, E-NRTLRK (Electrolyte NRTL Redlich Kwong) could most accurately fit VLE data of NH3-CO2-H2O system, with fitting error less than 1%. In the extent temperature range of 273.15 K-363.15 K, the prediction of product component using E-NRTLRK model for ammonia carbonation agreed well with the data reported in literature.
Co-reporter:Yanxia Xu, Xingfu Song, Ze Sun, Guimin Lu, Ping Li, and Jianguo Yu
Industrial & Engineering Chemistry Research 2012 Volume 51(Issue 1) pp:443-453
Publication Date(Web):November 22, 2011
DOI:10.1021/ie201147e
A hydrocyclone, as a common liquid/solid grading instrument, was chosen to separate calcium sulfate particles from crude carnallite during the KCl production process on the Tibetan Plateau in China, because CaSO4 particles are independent of KCl particles and have a smaller particle size distribution. The local altitude on the Tibetan Plateau in China is over 3000 m, so the effects of low atmospheric pressure on the separation performance of the hydrocyclone should be considered. In this article, the computational fluid dynamics (CFD) simulation technique was used to investigate the hydrodynamics and particles separation performance of an industrial hydrocyclone with a 428-mm diameter at both plain and plateau atmospheric pressures. In this CFD approach, the Reynolds stress model (RSM) was used to describe the turbulent fluid flow, the volume of fluid (VOF) multiphase model was used to simulate the interface between the liquid phase and the air core, and the stochastic Lagrangian model was used to track the particle flow. The mathematical models deveoped for the industrial hydrocyclone were tested by comparing the predicted results with the flow fields measured by Hsieh (Ph.D. Thesis, The University of Utah, Salt Lake City, UT, 1988). According to the simulation results, the environmental atmospheric pressures on the plain and plateau had effects mainly on the flow field inside the air core and near the interface between the air core and the liquid phase. It was found the direction of the axial velocity on the cylinder part and the values of the tangential velocity changed under the different environmental atmospheric pressures. When the industrial hydrocyclone was operated in the plateau environment, the separation efficiency for small particles decreased about 10% at the overflow, which was not good for CaSO4 removal, but there was no effect on the particles size larger than 350 μm, and more energy was consumed, although the difference in the split ratio was small.
Co-reporter:Xuemei Zhang, Xingfu Song, Ze Sun, Ping Li, and Jianguo Yu
Industrial & Engineering Chemistry Research 2012 Volume 51(Issue 18) pp:6563-6570
Publication Date(Web):April 12, 2012
DOI:10.1021/ie202203b
The reductive decomposition of calcium sulfate (CaSO4) to calcium sulfide (CaS) was one of the most important methods for anhydrite resource utilization. When CaSO4 was decomposed reductively by carbon monoxide (CO), usually there were CaS and/or calcium oxide (CaO) in the decomposition products of CaSO4 depending on the reaction temperature and reactant concentrations. In this paper, the mechanism of CaSO4 reductive decomposition by CO was studied in the framework of density functional theory (DFT). In the calculation, the exchange-correlation term was approximated by Perdew–Wang (PW91), a functional within the generalized gradient approximation (GGA) family. To study the interaction of CO and CaSO4, the transition states of CaSO4 decomposition and the minimum energy path (MEP) were analyzed. The results showed that the CaS product could be obtained when CaSO4 was reduced by CO with the 4:1 stoichiometric ratio of CO and CaSO4, and the decomposition of CaSO4 to CaSO3 was the rate-determining step, and activation energy in this step was 191.19 kJ/mol. With the increase of the reaction temperature, the CaO product could be obtained with a 1:1 stoichiometric ratio of CO and CaSO4, and the activation energy is 318.28 kJ/mol during the process. It was found that the CaS product was formatted at a lower reaction temperature and a higher mole ratio of CO and CaSO4, and the CaO product was preferred at a higher reaction temperature and a lower mole ratio of CO and CaSO4.
Co-reporter:Yuzhu Sun;Jin Wang ;Jianguo Yu
Crystal Research and Technology 2012 Volume 47( Issue 4) pp:437-442
Publication Date(Web):
DOI:10.1002/crat.201100571
Abstract
A spinning disk reactor (SDR) was used in this research to prepare Li2CO3 by gas-liquid reactive crystallization of LiOH and CO2. It was found that the end pH value of the above reaction should be controlled within the range of 9.0-9.5 to obtain a high yield of Li2CO3. The effects of operational parameters (including the temperature, the concentration of LiOH solution, the rotation rate of the spinning disk, the circulation rate of LiOH slurry, the flow rate of CO2 and the ultrasound field) on the particle size and the yielding rate were investigated by an orthogonal experiment. The results show the significant factors influencing the particle size are the ultrasound field, the temperature and the flow rate of CO2. As for the yielding rate, the temperature, the concentration of LiOH solution and the flow rate of CO2 exert obvious impacts, while the effects of ultrasound field and the rotation rate of the spinning disk are limited. The SEM images show the Li2CO3products are flower-like particles, which are composed of plate-like primary crystals. The size analysis shows the volume mean particle size of the Li2CO3products ranges 37-90 μm depending on the various experimental conditions. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Co-reporter:Yuzhu Sun;Jin Wang ;Jianguo Yu
Crystal Research and Technology 2011 Volume 46( Issue 2) pp:173-177
Publication Date(Web):
DOI:10.1002/crat.201000532
Abstract
Lithium carbonate (Li2CO3) hollow spheres were prepared by spray pyrolysis of lithium bicarbonate (LiHCO3) in this research. The products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), crystal size distribution (CSD) analysis and BET surface area measurement. The XRD figure of the product is nearly the same as the standard pattern, indicating the product achieved by spray pyrolysis has pure Li2CO3 crystalline phase. The SEM images show the self-assembly hollow spheres are composed of about 200 nm primary particles. While the CSD analysis shows the macro-volume mean crystal size ranges 4-9 μm depending on the experimental conditions. The BET surface area of the product reaches 7.24 m2/g, which is much higher than the best value reported in the literature. The product prepared in this work has great potential application prospect in the lithium-battery industry. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Co-reporter:Xingfu Song;Lina Zhang;Jingcai Zhao;Yanxia Xu;Ze Sun;Ping Li ;Jianguo Yu
Crystal Research and Technology 2011 Volume 46( Issue 2) pp:166-172
Publication Date(Web):
DOI:10.1002/crat.201000420
Abstract
Calcium sulfate whiskers, owing to its good thermal stability, chemical resistance and good compatibility with rubber and plastics, has a strong potential in the application of polymer reinforcing composite materials. This work deals with the preparation of calcium chloride whiskers by reactive crystallization process with sulfuric acid and calcium chloride discharged from Solvay process. Firstly, the orthogonal experiments were carried out using both CaCl2 and H2SO4 in analytic grade as feedstock, and the reactive crystallization conditions were optimized, which included reaction temperature, reactant concentration, reaction time and stirring speed. Based on the optimized reactive crystallization conditions, the new process for the preparation of calcium chloride whiskers was studied using the reactive crystallization process with sulfuric acid and calcium chloride discharged from Solvay process, and the effects of impurity ions in the waste solutions on the growth of whiskers were evaluated. It was found that calcium sulfate whiskers with stable and structured fine crystals (its aspect ratio up to 190) can be prepared using waste CaCl2 in Solvay process. The experimental results will provide the valuable information for the reasonable disposal of waste CaCl2 solution from Solvay process. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Co-reporter:Xingfu Song;Shuying Sun;Dengke Zhang
Frontiers of Chemical Science and Engineering 2011 Volume 5( Issue 4) pp:416-421
Publication Date(Web):2011 December
DOI:10.1007/s11705-011-1125-9
Magnesium hydroxide with high purity and uniform particle size distribution was synthesized by the direct precipitation method using MgCl2 and NaOH as reactive materials and NaCl as additive to improve the crystallization behavior of the product. The particle size distribution, crystal phase, morphology, and surface area of magnesium hydroxide were characterized by Malvern laser particle size analyzer, X-ray diffraction (XRD), scanning electron microscope (SEM) and Branauer-Emmett-Teller (BET) method, respectively. The purity of products was analyzed by the chemical method. The effects of synthesis conditions on the particle size distribution and water content (filtration cake) of magnesium hydroxide were investigated. The results indicated that feeding mode and rate, and reaction temperature had important effects on water content and the particle size distribution of the product, and sodium chloride improved the crystallization behavior of magnesium hydroxide. The ball-like magnesium hydroxides with the particle size distribution of 6.0–30.0 μm and purity higher than 99.0% were obtained. This simple and mild synthesis method was promising to be scaled up for the industrial production of magnesium hydroxide.
Co-reporter:Xingfu Song, Menghua Zhang, Jin Wang, Ping Li, and Jianguo Yu
Industrial & Engineering Chemistry Research 2010 Volume 49(Issue 21) pp:10297-10302
Publication Date(Web):September 9, 2010
DOI:10.1021/ie100786f
A computational fluid dynamics (CFD) model was developed for the simulation and optimization of an existing continuous DTB crystallizer with KCl productivity of 0.1 million tons per year. The multiple reference frame (MRF) method was used in the CFD simulation. Both the hexagonal grid and the tetrahedral grid were adopted to divide meshes in this industrial DTB crystallizer, and in total 866 388 cells were used for CFD simulation. The fluid flow field in the DTB crystallizer was calculated using FLUENT6.3 software with the Reynolds-averaged Navier−Stokes equation combined with the widely used κ−ε turbulence model. The crystal size distribution and the coefficient of variation of crystal product were studied by CFD simulation of two-phase flow model. The impeller shapes and various operating conditions were optimized to reduce the energy consumption of the crystallization process and to increase the KCl product quality. Based on the CFD optimization design, a new impeller was retrofitted into an existing continuous DTB crystallizer with the KCl productivity of 0.1 million tons per year located at Qinghai salt lake plant in China, and its excellent performance was confirmed against data collected using the original impeller.
Co-reporter:Yuzhu Sun, ;Jin Wang;Yan Luo ;Jianguo Yu
Crystal Research and Technology 2009 Volume 44( Issue 11) pp:1223-1229
Publication Date(Web):
DOI:10.1002/crat.200900402
Abstract
Dissolution of lithium carbonate (Li2CO3) in aqueous solution was investigated using three on-line apparatuses: the concentration of Li2CO3 was measured by electrical conductivity equipment; CLD (Chord Length Distribution) was monitored by FBRM (Focused Beam Reflectance Measurement); crystal image was observed by PVM (Particle Video Microscope). Results show dissolution rate goes up with a decrease of particle size, and with an increase in temperature; stirring speed causes little impact on dissolution; ultrasound facilitates dissolution obviously. The CLD evolution and crystal images of Li2CO3 powders in stirred fluid were observed detailedly by FBRM and PVM during dissolution. Experimental data were fitted to Avrami model, through which the activation energy was found to be 34.35 kJ/mol. PBE (Population Balance Equation) and moment transform were introduced to calculate dissolution kinetics, obtaining correlation equations of particle size decreasing rate as a function of temperature and undersaturation. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Co-reporter:Yuzhu Sun, Xingfu Song, Jin Wang, Yan Luo, Jianguo Yu
Journal of Crystal Growth (1 January 2010) Volume 312(Issue 2) pp:294-300
Publication Date(Web):1 January 2010
DOI:10.1016/j.jcrysgro.2009.10.036
The supersolubility data of Li2CO3 in the seeded aqueous solution were measured by focused beam reflectance measurement (FBRM). The effect of seed crystals on the supersolubility was investigated, where two kinds of seed crystals were considered, namely 2# seed with 318 μm volume mean crystal size and 5# seed with 21 μm volume mean crystal size, respectively. It was found that the supersolubility level of Li2CO3 in the presence of 2# seed is lower than that with 5# seed when using the same amount of seed; and with the increase of the seed loading, the supersolubility with 2# seed decreases slightly, whereas that with 5# seed becomes greater. The seeded supersolubility decreases when increasing both temperature and the stirring speed, and goes up with the increase of the feeding rate of Na2CO3. Moreover, by comparing the laser method with FBRM technology, FBRM is confirmed to be a better apparatus to detect the nucleation phenomena in the presence of seed.
Co-reporter:Yuzhu Sun, Xingfu Song, Jin Wang, Yan Luo, Jianguo Yu
Journal of Crystal Growth (1 December 2009) Volume 311(Issues 23–24) pp:4714-4719
Publication Date(Web):1 December 2009
DOI:10.1016/j.jcrysgro.2009.09.013
A laser aparatus was employed to investigate the unseeded supersolubility values of Li2CO3 in aqueous solution. It shows the supersolubility of Li2CO3 decreases with the raise of temperature and stirring speed, and with a reduction of feeding rate of Na2CO3. The introduce of ultrasound field leads to obvious reduction on supersolubility, whereas magnetic field causes little effect. The involving factors of impurities and additives on the supersolubility were also studied. It is found that the supersolubility value decreases with the addition of NaCl, KCl, NaNO3 and NaBr, while increases at the presence of Na2SO4, CH4N2O, NH4Cl, (NH4)2SO4 and EDTA disodium. Meanwhile, two mathematical models, empirical correlation and BP neural network, were used to simulate the supersolubility value as a function of temperature and feeding rate of Na2CO3. Compared with empirical correlation method, BP neural network simulation has better consistence with the experimental data.
